The D. melanogaster serpin protein minimum evolution tree. The serpin genes are distributed within the genome as a mixture of single transcripts and complex gene clusters. The complex loci tend to contain widely diverged transcripts, but Spn28Da/Spn28Db; Spn77Ba/Spn77Bb/Spn77Ba and Spn88Ea/Spn88Eb represent clusters of closely related transcripts. Inhibitory serpins are indicated with a solid black square, e.g.: Spn43Aa.